MOS Transistor Modeling for RF Integrated Circuit Design

Workshop on Compact Modeling Tutorial

Abstract

The design of radio-frequency (RF) integrated circuits in deep-submicron CMOS processes requires accurate and scalable compact models of the MOS transistor that are valid in the GHz frequency range and beyond. Unfortunately, the currently available compact models give inaccurate results if they are not modified adequately. This lecture presents the basis of the modeling of the MOS transistor for circuit simulation at RF. A physical and scalable equivalent circuit that can easily be implemented as a Spice subcircuit is described. The small-signal, noise and large-signal operations are discussed and measurements made on a 0.25 um CMOS process are presented that validate the RF MOS model up to 10 GHz.

Table of Contents

1. CMOS technology evolution: evolution of CMOS processes, process scaling, low-voltage constraint and its impact to RF CMOS circuit design.
2. Small-signal modeling: long-channel intrinsic small-signal parameters and their bias dependence, transcapacitances and non-quasistatic (NQS) effects, short-channel effects on small-signal parameters, extrinsic components (junction capacitances, series resistances, overlap capacitances), intra-device substrate coupling, y-parameters, ft and fmax, non-quasistatic versus quasistatic.
3. Noise modeling: thermal noise model, noise in short-channel devices, noise at HF, induced gate noise, HF noise parameters and their dependence on device geometry.
4. Large-signal modeling: evaluation of large-signal models at RF.